Subtypes and comorbidity in mathematical learning disabilities: Multidimensional study of verbal and visual memory processes is key to understanding.

A large body of research suggests that mathematical learning disability (MLD) is related to working memory impairment. Here, I organize part of this literature through a meta-analysis of 36 studies with 665 MLD and 1049 control participants. I demonstrate that one subtype of MLD is associated with reading problems and weak verbal short-term and working memory. Another subtype of MLD does not have associated reading problems and is linked to weak visuospatial short-term and working memory. In order to better understand MLD we need to precisely define potentially modality-specific memory subprocesses and supporting executive functions, relevant for mathematical learning. This can be achieved by taking a multidimensional parametric approach systematically probing an extended network of cognitive functions. Rather than creating arbitrary subgroups and/or focus on a single factor, highly powered studies need to position individuals in a multidimensional parametric space. This will allow us to understand the multidimensional structure of cognitive functions and their relationship to mathematical performance.

The experiential blink: Mapping the cost of working memory encoding onto conscious perception in the attentional blink.

The attentional blink (AB) represents a cognitive deficit in reporting the second of two targets (T2), when that second target appears 200-600 msec after the first (T1). However, it is unclear how this paradigm impacts the subjective visibility (that is, the conscious perception) of T2, and whether the temporal profile of T2 report accuracy matches the temporal profile of subjective visibility. In order to compare report accuracy and subjective visibility, we asked participants to identify T1 and T2, and to rate the subjective visibility of T2 across two experiments. Event-related potentials were also measured. The results revealed different profiles for the report of T2 versus the subjective visibility of T2, particularly when T1 and T2 appeared within 200 msec of one another. Specifically, T2 report accuracy was high but T2 visibility was low when the two targets appeared in close temporal succession, suggesting what we call the Experiential Blink is different from the classic AB. Electrophysiologically, at lag-1, the P3 component was modulated more by subjective visibility than by report accuracy. Collectively, the data indicate that the deficit in accurately reporting T2 is not the same as the deficit in subjectively experiencing T2. This suggests that traditional understandings of the AB may require adjustment and that, consistent with other findings, working memory (WM) encoding and conscious perception may not be synonymous.

ERP evidence of cognitive strategy change in motivational conditions with varying level of difficulty.

Recent research suggests that motivation improves cognitive functions but the particular mechanisms and precise behavioural conditions involved in such improvement still remain unknown. Particularly, it is unclear when in time and in which conditions these mechanisms are engaged. In the present study, we aimed to look at the neural markers of cognitive control strategies in different motivational conditions (motivation vs neutral) with different levels of difficulty (high vs low). Twenty-five adults completed a newly designed task in the four conditions above. Three ERP components were analysed: the CNV, LRP and P3b. We found that a motivational situation triggers the use of a proactive strategy when low cognitive control is required. A reactive strategy was used in a non-motivational situation and for difficult trials. Our study is also the first to provide evidence that the difference between proactive and reactive strategies occurs after the first stimulus (cue) is processed.